• Dai people, one of the 56 recognized ethnic minorities of China

• Da'i (Arabic: "missionary") refers to a person who engages in Dawah, the act of inviting people to Islam

• State of Dai was a Xianbei state during the Sixteen Kingdoms era of history of China

• Dai (Yindu), ethnic tribe of Chin, Myanmar

• Dai (大) is also a Sino-Japanese morpheme for "big," appearing in a number of Japanese words and names (and even a few pseudo-Japanese words, such as Daikatana)

• Dai is the greeting and farewell used by the wizards in Diane Duane's Young Wizards series.

• Dai County, in Shanxi, China.

Acronyms

• The DAI Personal Computer, an early (1980) home computer from Belgium.

• the New York Stock Exchange and Frankfurt Stock Exchange stock symbol for automaker Daimler AG (maker of Mercedes-Benz).

• Dangerous Anthropogenic Interference refers to changes in the Earth's climate system, resulting from human activity, which are considered to be dangerous to human communities and to ecosystems.

• Darjeeling Airport IATA code of Darjeeling airport in India

• De Administrando Imperio, a Byzantine historical compilation written by Emperor Constantine VII Porphyrogenitos

• German Archaeological Institute, an archaeological institute operated by the German ministry of foreign affairs

• the Deutsch-Amerikanisches Institut (German-American Institute)

• Diffuse axonal injury, a type of traumatic brain injury

• Digital Author Identification, Dutch Author Identification system to assign a unique number to all authors in the Dutch research system

• Direct Audio Input, a port used in hearing aids and hearing instruments

• Distributed artificial intelligence, a subfield of artificial intelligence

• Do As Infinity, a Japanese band

• Doctor's Associates, Inc., a U.S.-based restaurant company which owns the Subway restaurant name.

• Dynamic ARP Inspection, an ARP Spoofing or ARP Poison/Routing (APR) protection method developed by Cisco.

Names

• Dai is the Welsh diminutive form of David or its Welsh equivalent Dafydd

• Dai (戴) is a Chinese surname.

• Dai Davies (footballer)

• Dai Davies (politician)

• Dai Matsumoto, a Japanese voice actor

• Dai Nagao, Japanese composer, musician and producer

• Dai Satō, a Japanese screenwriter and musician

• Dai Ward, footballer